Kinematic Self-Replicating Machines
© 2004 Robert A. Freitas Jr. and Ralph C. Merkle. All Rights Reserved.
Robert A. Freitas Jr., Ralph C. Merkle, Kinematic Self-Replicating Machines, Landes Bioscience, Georgetown, TX, 2004.
4.19 Phoenix Primitive Nanofactory (2003)
Recognizing that molecular manufacturing requires more than just mechanosynthesis, in 2003 Phoenix  proposed a hierarchical system architecture for massively parallel assembly (Section 5.7) most directly in the lineage of the Drexler -Merkle  convergent assembly nanofactory system (Section 5.9.4) at the early (smaller) stages of the hierarchy and the Drexler  nanofactory system (Section 4.9.3) in the later (larger) stages of the hierarchy. According to the principal published paper , the Phoenix architecture combines large numbers of programmable mechanochemical fabricators, under computer control, into a manufacturing system or nanofactory. In addition to physical layout, Phoenix’s architecture and analysis includes some consideration of convergent assembly processes and simple mechanical connectors; thermodynamically efficient stepping drive mechanisms; redundancy and fault tolerance in fabricators and computers; product design, specification, and interpretation; product performance and cost; power budget, energy supply, and cooling; production, duplication, and bootstrapping times; and internal distribution of control information.
In a product cycle, each fabricator produces a 200-nm nanoblock, approximately the same size as the fabricator. (Blocks need not be solid cubes and their interiors may be quite complex.) These nanoblocks are then joined together, eight nanoblocks making one compound block twice as big. This process is repeated until the eight largest sub-product blocks are finally joined in an arrangement that is not necessarily cubical. The output of multiple product cycles may be combined to produce larger products. Products can be unfolded after manufacture, greatly increasing the range of possible product structures and allowing products to be much larger than the nanofactory that produced them.
At the lowest level, a few thousand fabricators are arranged in a planar workstation grid (Figure 4.56). Their products are picked up and assembled into progressively larger blocks by a series of increasingly larger robotic manipulators using guide rails and linear actuators. This plus a control computer constitutes a basic, reliable production module (Figure 4.57). In a production module, fabricators are positioned on two opposite faces, delivering their product nanoblocks to the interior. The nanocomputer occupies a third side, surrounding the product exit port. The remaining three sides may be closed by thin walls, but need not be closed at all between adjacent production modules. The interior is sparsely filled with gantry crane manipulators to assemble nanoblocks into larger blocks. Each production module produces a few product blocks, a few microns in size, by combining a few thousand nanoblocks. The production module includes multiple redundant fabricators interspersed throughout the fabricator arrays to permit multiple levels of fault tolerance in the event of fabricator failure or mechanochemical error.
Production modules are stacked three-dimensionally into gathering stages, which assemble blocks and pass them to higher-level gathering stages (Figure 4.58). Each gathering stage fits neatly into a rectangular volume, with substages arranged in two rows on either side of a central assembly and transport tube. At each stage, product blocks are delivered through the center of the narrowest face, allowing compact stacking of multiple production modules or stages. The substages, themselves rectangular structures, fit together with no wasted space in each row. The gathering/assembly tube contains simple robotic mechanisms to join the incoming product blocks into larger product blocks and deliver them out the end of the assembly tube . Space must be wasted between the rows, adjacent to the central tube, because this is a physically simple architecture.
Because the nanofactory is built with primitive fabricators and control systems, it is expected to use a lot of energy and can be cooled using a working fluid containing suspended encapsulated ice particles as originally proposed by Drexler . Molecular feedstock for mechanosynthetic processes is also dissolved in the working fluid. Gaps are left for fluid channels adjacent to the fabrication arrays of the production modules, providing each fabricator with direct access to feedstock and, if necessary, flowing solvent to remove waste. As production modules are stacked, the cooling channels line up – the overall arrangement is a quasi-fractal working volume interpenetrated by a non-fractal cooling channel volume. Power and signals are routed through the walls of the transport tubes, since the end of every transport tube touches the side of the next-larger tube. Each stage joins eight blocks to form one block with twice the linear dimension, so 19 stages are required to progress from a 200-nm nanoblock to a 10.5-cm product, plus one additional stage (a simplified gathering stage) that is used to transition from production modules to gathering/assembly stages .
Finally, the entire factory is enclosed in a suitable casing with a mechanism to output final product without contaminating the workspace. In the highest level nanofactory layout, the overall nanofactory shape is a rectangular volume (Figure 4.59). The exterior shell consists of six flat panels, with each panel: (1) providing support to anchor the interior and prevent the working volume from collapsing under atmospheric pressure, and (2) supporting each other. Panels are hollow and pressurized, held rigid and flat using internal tension members set at a slight angle. The design is easily scalable to tabletop size, with a ~1 meter factory producing eight ~5 cm blocks per product cycle. A tabletop nanofactory measuring 1 meter x 1 meter x 0.5 meters might weigh 10 kg or less (without coolant), produce 4 kg of diamondoid (~10 cm cube) in 3 hours, and could require as little as twelve hours to produce a duplicate nanofactory .
Last updated on 1 August 2005